I like that this is a little more controlled than Ruhan of the Fomori, since you can at least scale the damage
Its essentially a Seaside Citadel, but you can put it directly into play by paying and returning a tapped creature (web-slinging, basically)
Its a bold choice that prioritizes flavor over the traditional standard landscape aesthetic, making these cards instant conversation starters at any Commander table
Sheoldred, the Apocalypse Sheoldred, the Apocalypse is utterly terrifying, and that goes for any format
If youve played for a while, or have invested in getting the older cards in Arena, you might look into building a competitive deck in Historic, Explorer, or Pioneer
I think Giver of Runes is a fine inclusion in any deck that wants a second copy of Mother of Runes